Compaction machines are frequently employed for compacting fresh laid asphalt, soil or other compactable materials. One such type of compaction machine is a drum-type compactor having one or more drums that compacts material over which the compactor is driven. In order to compact the material, these drum-type compactors include a drum assembly having a vibratory mechanism.
In U.S. Pat. No. 8,556,039 to Marsolek et al., the vibratory mechanism includes inner and outer eccentric weights arranged on a rotatable shaft or a key shaft. The key shaft is positioned within an inner cavity of the inner eccentric weight such that as the key shaft rotates, it causes the rotation of the inner and the outer eccentric weights to induce vibrations on the drum for compacting material. In order to facilitate rotation of the inner and the outer eccentric weights, the outer surface of the key shaft is provided with axial or straight splined portions that engage with the inner eccentric weight, as well as helical splined portions that engage with the outer eccentric weight to facilitate rotation of those eccentrics. A linear actuator reciprocates the key shaft during operation.